P1.9
Variations in surface tubulence characteristics over the Salt Lake Valley during VTMX2002
J. C. Doran, PNNL, Richland, WA
Characterizing vertical mixing processes and improving their representation in numerical models is one of the main objectives of the VTMX program. As part of that effort, nocturnal turbulence characteristics at several sites in the Salt Lake Valley during VTMX 2000 in October 2000 are compared using data obtained from sonic anemometers. The sites included one near the middle of the valley, a second location on the southwestern slope of the valley about 120 m higher, and a third site in the Jordan Narrows at the south end of the valley. Sensible heat fluxes at the mid-valley site, which was often affected by a shallow, strongly stratified layer on the order of 100 m in depth, were generally weak and frequently intermittent but consistently downward. In contrast, the fluxes at the other two sites were much more variable. Frequent episodes of small upward heat fluxes were found at the slope site, beginning around midnight LST and coinciding with a decrease in the downslope wind speed. At the Jordan Narrows site, negative sensible heat fluxes in excess of 50 W m-2 developed several hours after sunset in conjunction with an increase in wind speed and a rise in air temperature at the level of the sonic anemometer (9 m). A discussion of possible mechanisms accounting for the observed behavior and implications for numerical simulations of turbulent exchange near the surface is given.
Poster Session 1, PBL Processes and Modeling (with Coffee Break)
Monday, 17 June 2002, 2:45 PM-4:15 PM
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